For me the combat system of both games was kinda hit and miss
Mass Effect 1, the overheat system meant ammo was no problem (i often found myself running low on crucially needed ammo on ME2) and the hybrid classes were a lot more balanced, for example the Vanguard felt like a happy medium between Soldier and Adept, whereas ME2 took away a lot of biotic abilities and essentially made Vanguard a close range Soldier, which would be ok if your health didn't drop faster than a whore's knickers. But Mass Effect 1 had a lot of drawbacks. Overabundance of armour/weapons/gun upgrades/ammo upgrades found on dead enemies was annoying, and the sniper is godawful until you get training, unlike the other weapons which start of pretty decent and develop into very good weapons.
Mass Effect 2 had problems too. Select ammo abilities only available to certain classes (unless you chose the soldier, then you pretty much had all of them) The SMG sucked, and the mix and match system with armour, while good i often asked myself "do i need this stat or that one?" However ME2 fixed the sniper rifle, introduced some kick-ass heavy weapons, the ability to choose more than one ability at once for the squad
Classes on ME1 in my opinion were kind of crap. the short story was, because of the stupidly long recharge times for powers, best choice was going for a soldier, or a soldier hybrid. (personal preference being Vanguard) ME2 technically fixed this. The classes were tuned to be more-or-less equal with each class having a signature ability defining it from the rest. however, a lot of classes lost abilities (Vanguards lost Barrier. not cool) and some of the signature moves were pretty crap, notably the Vanguards Charge ability. sure it looks awesome, but if there's a group of enemies you didn't notice when you pull it off, you get swiss cheesed. plus, the decision to make Vanguard "a close quarters combat specialist" was pretty stupid considering it's a cover based shooter.
